The various methods of preparing an arenethiol from the corresponding phenol are described in Rodd's Chemistry of Carbon Compounds, Supplement to Volume III A (published by Elsevier in 1983), at pages 247 to 249. The recommended procedure is the Newman-Kwart rearrangement in which the phenol is reacted with a dialkyl thiocarbamoyl chloride, then heated and hydrolysed. A paper by Y. Araki in Bull. Chem. Soc. Japan 1970 43 pp 252-257 is reported; Araki describes the thermal rearrangement of O,S-diaryl dithiocarbonates to S,S-diaryl dithiocarbonates, which can be hydrolysed to form thiophenols. The O,S-diaryl dithiocarbonates are prepared by the reaction of a substituted phenol with an aryl chlorodithioformate. Japanese published unexamined patent application 49-70926 describes the rearrangement of O,S-diaryl dithiocarbonates to S,S-diaryl dithiocarbonates by catalysts which contain aluminium chloride in at least equal molar amounts in carbon disulphide.
An alternative known procedure is the Schonberg rearrangement: ##STR1## (where Ar represents an aryl group) This procedure has the disadvantages that only half the phenol used can be converted to arenethiol (yields are much lower in practice), the noxious chemical thiophosgene is required and the separation of equal amounts of arenethiol and phenol is difficult. The corresponding O-aryl O-alkyl thiocarbonates do not rearrange when heated; they lose carbonyl sulphide to form an aryl alkyl ether. Similarly S-aryl O-alkyl dithiocarbonates lose carbonyl sulphide on heating, forming an aryl alkyl thioether.